1. Field of the Invention
This invention relates to a second-harmonic generation device and a method of producing the same and a second-harmonic generation apparatus and a method of producing the same.
2. Description of the Prior Art
A waveguide type of a second-harmonic generation device is known. Such a harmonics generation device emits a second harmonics generated by waveguiding a fundamental wave incident thereto. There are a lot of researches for improving the efficiency of converting the fundamental wave to the second harmonics. However, there is a problem that a considerable amount of noise is developed in the laser light from a semiconductor laser which generates the fundamental wave incident to the second harmonics generation device. This is because the laser light from the semiconductor laser is reflected at an inlet of a waveguide of the second harmonic generation device and returns to the semiconductor laser. The reflected light induces the noise.
A second harmonic generation apparatus is known. Such a harmonics generation apparatus comprising a semiconductor laser for generating a fundamental wave ray, the second harmonics generation device mentioned above for generating a second harmonics ray, and an optical system for introducing the fundamental wave ray (laser light) to the second harmonics generation device. The second harmonics device generates the second harmonics in response to waveguiding a fundamental wave incident thereto. However, there is a problem that a considerable amount of noise is developed in the laser light from a semiconductor laser which generates the fundamental wave incident to the second harmonics generation device. This is because the laser light from the semiconductor laser is reflected at an inlet of a waveguide of the second harmonic generation device and returns to the semiconductor laser. The reflected light induces the noise.
In the prior art second harmonics generation device and second harmonics generation apparatus, there are a considerably large amount of noise in the fundamental wave ray because the noise is developed by the light reflected in the waveguide of the second harmonics generation device and the second harmonics generation apparatus returning to the semiconductor laser. Accordingly, the mode hopping phenomenon or other adverse phenomenon occurs, so that the second harmonics includes a considerably large amount of noise and its output is unstable.